The traditional methods of attaching the tubing string to a production packer or other completion equipment rely on devices known as seal assemblies. These assemblies allow the production tubing to maintain a continuous sealing conduit for the purpose of oil and gas production up the inside of the tubing and further allow the ability to disconnect the tubing when desired. The seal assemblies are normally connected to the packer in one of two ways, floating or anchored.
The floating seal assembly, also known as a locator seal assembly, is designed to allow for thermal expansion and contraction of the tubing without adding high stress to the tubing string. The seal assembly simply floats in a polished-bore receptacle (PBR) during the production life of the well.
It is more often desirable to anchor the tubing to the packer completion to ensure tubing stability. This is particularly true in the case of some deepwater completions where a tension leg platform is used. For safety reasons, if a surface failure occurs, such as the platform floats off location and pulls an extreme tension load on the well, the desire is to have the tubing resist this tension by staying anchored to the completion packer. Therefore, the anchor seal assembly is attached to the packer via a threaded connection. Typically, the anchor seal assembly is removed from the packer by means of rotation at the surface or shear release. However, most deepwater completion designs have a significant number of control lines strapped to the outside of the tubing string. Some of these wells are highly deviated, making rotation difficult.
The current method of releasing an anchor in this type of completion is to run through the tubing with an internal tubing cutting assembly to a location just above the anchor seal assembly and cut the tubing completely through. The tubing is then removed. A second trip is then made with a work string to grapple and rotate the anchor out of the completion packer. Once the anchor is removed, a packer retrieving tool can be run to depth to recover the packer. This procedure requires a minimum of three round trips and is very expensive. Rig time in deep-water completions can run over $150,000 per day. Often, several days may be needed to recover the packer in this traditional manner.
In other situations, there arises a need to pull the tubing with the packer to facilitate further downhole operations. This is to be contrasted with dealing with a situation such as a leak in the tubing above the packer, which would not require the removal of the packer. In situations where not only the tubing needs to come out but the packer as well, the prior technique involved going thru-tubing with a tubing cutter to cut the tubing and retrieve the portion of the tubing above the cut. A second trip was required to remove the anchor for the tubing in the packer, and then a third trip was required back into the hole with a retrieving tool so that the packer could be retrieved. The retrieving tool had to be a specific length and have a defined latch to mate up with the packer receptacle assembly which is in the hole. The third trip would involve moving a support ring out from under a collet assembly on the packer, which unlocks the slips and sealing element of the packer and enables the tool to be retrieved with a pulling force.
Thus, in both situations the objective is to be able to accomplish the removal of the tubing only or of the tubing and the packer in fewer trips in the wellbore, thus saving rig time.
Hydraulic release mechanisms, as between the packer and the tubing, have been used in the past. However, the disadvantage of such designs is that they created leak paths between the tubing and the annulus if any of the various O-rings that are required in such designs malfunction. Thus, what is needed is a design which does not have the limitations of hydraulic release techniques as between the tubing and the packer; one such design provides for metal-to-metal sealing components. Thus, one of the objectives of the present invention is to provide a design which does not have the potential leak paths yet at the same time allows for simple separation of the tubing from the PBR without any need for twisting or turning. The objective is met with a design that allows, in a single trip in the hole, the actuation of the release mechanism to separate the anchor seal assembly from the PBR via an internal punch tool. Alternatively, the packer can be released thru-tubing with a retrieving tool which can go thru-tubing to the packer and act on its release assembly and following the operation, be readily removed. With the packer released, it can then be retrieved as the tubing is pulled out of the hole, thus eliminating the time required to pull the tubing to retrieve the packer.